It is dangerous to ignore SkRect::intersect's return value

gm/offsetimagefilter.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "gm.h"
 #include "SkOffsetImageFilter.h"
 #include "SkBitmapSource.h"
@@ skipping 64 matching lines @@
         SkPaint strokePaint;
         strokePaint.setStyle(SkPaint::kStroke_Style);
         strokePaint.setColor(SK_ColorRED);
 
         // Draw a boundary rect around the intersection of the clip rect
         // and crop rect.
         SkMatrix scaleMatrix;
         scaleMatrix.setScale(scale, scale);
         SkRect cropRectFloat;
         scaleMatrix.mapRect(&cropRectFloat, SkRect::Make(cropRect));
-        clipRect.intersect(cropRectFloat);
-        canvas->drawRect(clipRect, strokePaint);
+        if (clipRect.intersect(cropRectFloat)) {
+            canvas->drawRect(clipRect, strokePaint);
+        }
     }
 
     virtual void onDraw(SkCanvas* canvas) {
         if (!fInitialized) {
             make_bitmap();
             make_checkerboard();
             fInitialized = true;
         }
         canvas->clear(0x00000000);
         SkPaint paint;
@@ skipping 27 matching lines @@
     SkBitmap fBitmap, fCheckerboard;
     bool fInitialized;
 };
 
 //////////////////////////////////////////////////////////////////////////////
 
 static GM* MyFactory(void*) { return new OffsetImageFilterGM; }
 static GMRegistry reg(MyFactory);
 
 }